This invention relates to a means for shaping fiber-reinforced articles. In one of its more specific aspects, this invention pertains to a means for shaping glass reinforced fibrous mats using double preform screens with moveable presser rods. The shaping means is particularly suitable for the manufacture of automobile bumper reinforcements.
The production of glass fiber-reinforced materials into useful shapes is well-known. Normally the glass reinforced fibrous mat is preformed and then placed in a mold for shaping into a final product. Typically, glass fiber reinforced mats are used in situations where a desired strength of the reinforced mat is necessary, such as in automobile bumpers. For example, layers of the glass fiber-reinforced mat are fabricated separately and then combined in a mold to make the final product. The mat layers are fabricated using a set of preform screens which consist of an upper and a lower screen where each screen is stretched to conform to the shape of the final product. The top screen stretches and bends the glass fibrous mat to conform to the shape of the bottom screen. However, such preform screens can cause problems wherein the screens often undersirably stretch the glass fiber-reinforced mats beyond acceptable limits causing the mats to thin out or tear. Also, the preform screens do not always position the fiber mat into the far corners of the mold, causing "radius bridging" wherein the corners are slightly rounded or incomplete.
The production of articles from glass fiber preform mats in such manner is a time-consuming process since the manufacture of a preform normally includes at least a two-step operation: first, layers of initial preform material are prepared; and second, the layers of additional preform material are placed into a mold and then cured to form a final product. In addition, the currently used means for producing the fiber-reinforced mats cause difficulty in handling of the preform materials both during the manufacturing process and the preforming process.
Considerable time and expense would be saved if a glass reinforcement preform product could be made in a high speed operation which entails only one fabricating operation instead of two separate operations.
It would be beneficial if various combinations of different fibrous reinforcement materials could easily be fabricated into final preform products.
Further, it would also be beneficial if glass fibrous reinforced products could be made without compromising the integrity of the final product, either by stretching of the fiber-reinforced mat during the shaping process or by thinning of the corners of the mat caused by radius bridging during the shaping process.